This invention relates to a recording device such as a so-called electronic blackboard. Recording devices like an electronic blackboard have been known. With such a device, the user draws characters and figures on a white sheet-like member by using a pen, for example, and such characters and figures are subsequently exposed to light. The reflected light from the sheet-like member is passed through an optical system including a lens and is received, for example, by a solid image accepting unit. Output signals from such a unit are stored in memory buffer in the form, for example, of a random-access memory (RAM) and are used for thermal recording through electric circuits of various types. With electronic blackboards of conventional types, only so-called thermal recording paper sheets can be used for thermal recording and this has a limiting effect on the multi-purpose characteristics regarding recording medium. Moreover, accuracy of displayed characters and figures by thermal recording on a recording sheet is determined by the number of heat-emitting elements in the recorder, or the so-called thermal head, with which recording is effected on a thermal recording sheet as well as the size of the individual heat-emitting elements. If it is desired to improve the accuracy and quality of a display, therefore, an increased number of smaller heat-emitting elements must be used. This will cause the device to become complicated in structure. Furthermore, prior art technologies of this type required complicated processing of digital signals.